Autometer speedo to vss signal?

[mrhurt73]

i was digging on autometers website and i found the spec sheet for my speedometer, this maybe a lot easier than i thought.

but my question is Pin 21 on the red connector the right terminal?
my computer is 5.3L Gmc 2000 truck for reference.

[ls1nova71]

I don't know why Autometer says to hook it directly to the speed sensor, but if you do, it can cause some problems. On mine it screwed with the signal going to the PCM, and therefore would cause erratic shifting at high MPH's. Hook the speedometer signal wire to the VSS output from the PCM, red connector C2 pin #50 dark green with a white stripe. You WILL have to calibrate it before it will work, but it does work. Then when you calibrate it, and the odometer counts off pulses per mile, either drive the 2 miles, or just stop when it gets to 4000 ppm. If your tune is correct, the speedo will be also. Stopping at 4000 ppm will show on the speedometer exactly what the PCM is reading.

[mrhurt73]

Originally Posted by ls1nova71

I don't know why Autometer says to hook it directly to the speed sensor, but if you do, it can cause some problems. On mine it screwed with the signal going to the PCM, and therefore would cause erratic shifting at high MPH's. Hook the speedometer signal wire to the VSS output from the PCM, red connector C2 pin #50 dark green with a white stripe. You WILL have to calibrate it before it will work, but it does work. Then when you calibrate it, and the odometer counts off pulses per mile, either drive the 2 miles, or just stop when it gets to 4000 ppm. If your tune is correct, the speedo will be also. Stopping at 4000 ppm will show on the speedometer exactly what the PCM is reading.

well thats what i wondered, i have pin 50 marked on my harness. that would be real easy to wire into.

driving the 2 measured miles would be easy using interstate mile markers, thats how i did it the first time. its easy where i live, no traffic to be in the way on the interstate.

but how would i know i reached 4000 ppm? software on the OBDII port maybe?

[ls1nova71]

Mile markers are only semi accurate, but they will get you close. But to set it by the PPM, if your odometer is digital, and I think most Autometer electric speedos are, will count off the pulses when in calibration mode. If you set it that way, your info in the tune has to be correct also, tire size, gear ratio ect.

[mooseknuckles]

I have autometer elec. gauges and for the life of me can't get the speedo calibrated correctly....I done the 2km thing a hundred times and it still reads 30 km too high. I begining to think PSI has effed something up! I have the correct gears and tires size in my handheld tuner.....the gps says 81kph, and the speedo's around 110kph